Two Occurrences of Leukemia Relapse Due to Mismatched HLA Loss After Haploidentical Stem Cell Transplantation From Different Family Donors With KIR Ligand Mismatch.

Mismatched HLA loss is a cause of leukemia relapse after HLA-haploidentical stem cell transplantation (haplo-SCT). We report a patient with a history of 2 occurrences of leukemia relapse due to mismatched HLA loss after haplo-SCT. He received haplo-SCT from his father but showed leukemia relapse with loss of the maternal HLA haplotype. He then underwent haplo-SCT from his mother, and developed relapse with loss of the paternal HLA haplotype. Both donors had killer cell immunoglobulin-like receptor-ligand mismatch but alloreactive natural killer cells could not prevent relapse. Second haplo-SCT should be conducted carefully for patients with relapse due to mismatched HLA loss.